I am brand new here but this topic caught my eye as I am about to deal with some surface frame rust and some very light surface rust on the back of a door panel and body support on a Excursion. I have read every post with great interest.
What I have gathered from reading everything here is the following:
I see little controversy on here that Ospho does a good job of protecting or converting rust.
It seems the main and really only point of contention is whether Ospho leaves an acid film or not. Now specifically to this thread its a bit more detailed. We are speaking specifically if there is an acid film left when following the direction and procedures as laid out by DBM.
Is there some reason you can not just use a 0-14 PH testing strip on the metal surface after all the steps DBM does prior to spraying primer and see what you get?
Seems like a really simple and 100% way to put this to bed. I can not see how there could be any argument if the PH comes back somewhere around in the middle of the PH range. A 85% Phosphoric acid solution has a PH of about 0.5 PH so we are not talking some small change here.
My bet is that there is a differnce between Ospho leaving a acid film after dry vs following DBM steps and procedures there is an acid flim left from Ospho once you reach the primer spray step.
Basically it seems to me there can easily be a difference between soaking the metal with Ospho letting it dry
Now ready for epoxy primer and checking the surface PH
Soaking the surface with Ospho waiting wiping away any pools or drips any excess at all with a towel.
Sanding or scuffing the entire surface
Wiping off clean with a rag soaked in wax & grease remover (I think this may have a big effect)
Allowing to dry
Now ready for Epoxy Primer and testing surface PH level.
Its seems pretty straight forward and definitive to me but I am about as novice to painting as can be. Tons of experience Hot Parkerizing/Phosphating firearm parts for years but automotive industrial painting and prep Nope NADA NOT.
This looks like a much better choice for a person like me than a first time hobbyist than many of the other options out there. It will allow me to do sections at a time as I can. I can get it into hard to reach areas as taking some of these body panels off is not possible and or way to much involved for a daily driver. I just want to put to be sure I will not find a rotted out body panel under the undercoating in a few years. I live in the mountains of VA ( well we call them mountains here on the east coast) so we see salt and wet salt solution road prep during the winter months. I need to get the under carriage exposed surfaces sealed from this attack as best as I can.
I want to personally thank you for spending so much of your free time attempting to educate others on the system you have used and found to work well. I have found it very helpful. But then I am very good at following directions. LOL